Figure 1
From: Ectosymbionts alter spontaneous responses to the Earth’s magnetic field in a crustacean
Magnetic alignment of crayfish. We tested spontaneous magnetic alignment behaviour of crayfish in a baseline assay without prior manipulation of ectosymbiont densities (A). We split the distribution of crayfish alignments based on symbiont densities above (high) and below (moderate) the median value of 5 worms (B). We also tested magnetic alignment behaviour of crayfish with manipulated worm densities at three treatment levels; no worms, moderate and high worm density (C). Baseline test demonstrated a significant magnetic alignment of crayfish to the magnetic NE/SW axis. Crayfish with moderate worm densities exhibited a bimodal distribution of alignments with respect to the magnetic field, whereas those with high worm densities were not magnetically aligned. Crayfish tested with three different ectosymbiont densities showed a quadramodal distribution of alignments when hosts were without worms ‘no worms’, a bimodal distribution of alignments when hosts had a moderate worm density, and a distribution of magnetic alignments that was indistinguishable from random when hosts had a high worm density. Significance of alignments was tested by the Rayleigh-test; p-value (p), sample size and the mean vector length (r) are given for each distribution. We compared distributions using the Watson U2-test; test statistic (U2) and p-values are shown above the arrows indicating the compared distributions. All p-values with an asterisk are alpha corrected, when tested for axial and bi-axial alignment. We calculated a 95% confidence interval around the mean direction confidence interval in case of significance.
